BEHAVIORAL AND INTEGUMENTARY CHANGES ASSOCIATED WITH INDUCED METAMORPHOSIS IN DIEMICTYLUS

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Abstract
1. After larval metamorphosis the eft (terrestrial) phase of Diemictylus viridescens can be induced to undergo second metamorphosis to the aquatic, adult phase with mammalian prolactin. In the present investigations adults receiving thyroxin (10 to 20 µg. every other day) showed a partial reversal to second metamorphosis by migrating to land. However, the thin, cornified epidermis did not approximate the granular and compact eft-like epidermis seen in adults which were maintained without treatment in a terrestrial environment. 2. Ovine prolactin (NIH) produced water migration in efts and inhibited primary metamorphosis in larvae, while maintaining the smooth, compact epidermis characteristic of the normal adult. 3. Reaction of adult skin fragments in tissue culture receiving either 0.2 mg./ml. thyroxin or 1 mg./ml. prolactin paralleled the above results: after several days thyroxin-treated skin had lost most of its structural organization as compared with controls while prolactin cultures were well maintained, with a compact epidermis which even molted on several occasions. 4. Iodine-131 uptake of land-maintained adults showed values (12.07±0.9%) which approached those for efts, as compared to the low values for normal adults and prolactin treated efts. 5. The evolution of a prolactin-thyroxin axis during the course of vertebrate evolution is suggested. Thyroxin may have affected adaptation to terrestrial environments and prolactin adaptation to the fresh-water habitat. Although the early activity of prolactin may be associated with the water-drive principle, it is understood that changes in tissue response or in the structure of prolactin have greatly extended the range of action for prolactin (prolactin-like principles) in higher vertebrates.